Chronic inflammation is thought to be a major factor in atherosclerosis, cancer, and aging. Acute inflammation (activation of the immune system and the release of inflammatory cytokines) occurs in the presence of infection and vaccination. Hence, the authors of a newly published paper1 undertook a study of the association between heart attack and stroke and the occurrence of acute infection and vaccination through the United Kingdom General Practice Research Database of computerized medical records for over 5 million people.

Among 20,486 people who had a first heart attack and 19,063 people who had a first stroke who had received influenza vaccine, there was no increase in the risk of heart attack or stroke in the period after influenza, tetanus, or pneumococcal vaccines. However, the risks were substantially greater after a diagnosis of systemic respiratory tract infection, with the risk particularly high during the first three days. The risks of heart attack or stroke were raised significantly, but to a lesser extent than systemic respiratory tract infection by urinary tract infection. A separate paper reports that periodontitis, a source of chronic inflammation, reduces the antiatherogenic effects of high-density lipoprotein (HDL),2 thereby potentially increasing the risk of heart attack or stroke.

These results are not surprising in the face of earlier findings that inflammatory markers such as C-reactive protein are good indicators of cardiovascular risk. The authors of this paper1 also note that an increased leukocyte count “may herald a short period of increased risk of stroke.”